Aperture vessel for fluid-suspension particle analyzer

ABSTRACT

Improved aperture vessel is provided for processing a sample of fluid-suspended particles through an aperture during the study of particle characteristics such as size distribution. Vessel may be used with commercially available particle analyzers such as the Coulter electronic, electro-optical and similar types of particle analyzing apparatus. Vessel construction permits a large fraction of sample suspension to be drawn from a sample beaker, through a particle aperture and an aperture chamber, and then into a calibrated volume-measuring bulb. The aperture chamber has an open bottom which, together with a series of associated valves, enables full recovery of the sample suspension fluid as well as both suspended and unsuspended particles after passing through the aperture. This aloquot is recovered in a transfer flask and recycled into the sample beaker. Since the study procedure is quantitative, unlimited numbers of data points are now obtainable on each sample. Greatly improved counting statistics are obtained on samples that contain very few particles of a given size.

Elite States Patet Flinchbaugh [451 Apr.4,1972

[541 APERTURE VESSEL FOR FLUID- SUSPENSION PARTICLE ANALYZER [72] Inventor:

[52] US. Cl. ..324/71CP, 73/4256 [51] Int. Cl. ..Goln 27/00 [58] Field oi'Search ..324/71 CP, 71 LC; 73/421 B, 73/422, 425.4, 425.4 P, 425.6

[56] References Cited UNITED STATES PATENTS 3,453,438 7/1969 Ban et al. ..324/71 CP 3,554,037 1/1971 Berg ...324/71 CP 2,434,723 l/l948 Shook ..73/425.4 P 3,361,965 1/1968 Coulter et al. ..324/71 CP 2,995,037 8/1961 Parker et a1 ..73/421 B 3,015,775 1/1962 Coulter et a1. ..324/71 CP 3,188,565 6/1965 Kolb ..73/422 UX 3,395,343 7/1968 Morgan et a1 ..324/71 CP A TMOSPHERE Primary Examiner-Rud0lph V. Rolinec Assistant ExaminerR. J. Corcoran AtlorneyJoseph J. OKeefe 5 7] ABSTRACT Improved aperture vessel is provided for processing a sample of fluid-suspended particles through an aperture during the study of particle characteristics such as size distribution. Vessel may be used with commercially available particle analyzers such as the Coulter electronic, electro-optical and similar types of particle analyzing apparatus. Vessel construction permits a large fraction of sample suspension to be drawn from a sample beaker, through a particle aperture and an aperture chamber, and then into a calibrated volume-measuring bulb. The aperture chamber has an open bottom which, together with a series of associated valves, enables full recovery of the sample suspension fluid as well as both suspended and unsuspended particles after passing through the aperture. This aloquot is recovered in a transfer flask and recycled into the sample beaker. Since the study procedure is quantitative, unlimited numbers of data points are now obtainable on each sample. Greatly improved counting statistics are obtained on samples that contain very few particles of a given size.

9 Claims, 4 Drawing Figures VACUUM PART/CL E SIGNAL ANALYZER Patented April 4, 1972 3,654,551

2 Sheets-Sheet l VACUUM ATMOSPHERE R F PARTICLE /g SIG/VAL ANALYZER INVENTOR Dean A. F l/hchbaugh Patented April 4, 1972 3,654,551

2 Sheets-Sheet 2 PARTICLE SIG/VAL ANALYZER as as Q INVENTOR Dean A. F/fnchbaugh APERTURE VESSEL FOR F LUID-SUSPENSION PARTICLE ANALYZER BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates broadly to fluid-suspension particle analyzing apparatus. More particularly, it relates to vessel construction for processing and recycling a sample of fluidsuspended particles through an aperture during the study of particle characteristics, such as size distribution, by a particle analyzer.

2. Description of the Prior Art In many scientific and industrial applications, it is desirous and sometimes mandatory to determine particle characteristics, such as size distribution, of constituent parts of a variety of solid and fluid bodies. For example, in the manufacture of steels, it is necessary to know the particulate inclusion content of a heat of steel, or even an ingot thereof, as certain inclusions of sufficient size and quantity have an adverse effect on the physical properties of subsequently rolled steel products. Further, in the preparation of particulate materials it is often necessary to grind solid stock to a specified particle size distribution. Moreover, in pollution abatement work it is necessary to know the size and count of pollutants in streams and/or the atmosphere in order to take appropriate corrective measures. Thus, it is apparent that the determination of particle characteristics is necessary in order to cope with the foregoing situations.

Generally, commercially available apparatus for studying particle characteristics include the well known Coulter electronic type as well as electro-optical, ultrasonic and other types of particle analyzing apparatus. The present invention will be described hereinafter with reference to the Coulter type apparatus, although it is also applicable to the other types of apparatus.

Construction and operation of the Coulter apparatus is disclosed in U.S. Pat. No. 2,656,508. Briefly, the Coulter apparatus involves a scanner element having an aperture for detecting particles electrically and an electronic instrument responsive to the scanner for measuring and indicating size distribution of powdered materials, i.e., the particle count in each of numerous volume ranges in a total population of particles. When all test particles are assumed to have the same unit weight, as they generally do, then there is a direct relationship between particle volume and particle size. Hence, the latter term is referred to hereinafter.

In operation, a sample is prepared by suspending the particles to be analyzed in a conductive fluid and maintaining a uniform particle distribution by stirring, otherwise the heavier particles may tend to settle out of an unstirred solution. A small fraction of the sample suspension is drawn from a first chamber into a second chamber through a small aperture, or orifice, by means ofa vacuum applied to the second chamber. Suspension flow is metered by a mercury manometer. An electrode is placed in each chamber and these electrodes together with the aperture and second chamber comprise the scanner element.

An electrical current, generated by the instrument and established in the fluid suspension between the electrodes, is altered momentarily when a particle passes through the aperture. This phenomenon is disclosed in Coulters U.S. Pat. No. 2,985,830. A commercially available particle analyzer which utilizes this phenomenon is the Coulter Counter, Model B-M including a volume converter which automatically converts basic counter information into volume percent or weight percent readout. The change in electrical current is detected in the instrument portion of this apparatus as a pulse in a discriminating circuit having calibrated level adjustments. The magnitude of the pulse is proportional to particle volume. Therefore, each calibrated discriminating level, together with various calibrated sensitivity levels, correspond with, and indicate to an attendant, a predetermined particle size range. The number of pulses correspond to the number of particles of the indicated size range and this number is registered on a counter which is also included in the instrument. The counter is normally started and stopped manually, or automatically by corresponding signals from the mercury manometer when a prescribed volume of suspension, corresponding to the small fraction of the sample, is caused to flow through the aperture. Execution of data taking sequences involving different particle size ranges during successive runs of fractions of the sample will ultimately enable a particle size distribution to be tabulated or plotted.

Although the Coulter particle analyzing apparatus has gained widespread acceptance and met with success, it possesses a number of inherent disadvantages to users requiring analysis of voluminous, expensive and/or hazardous samples. For example, when passing the fluid suspension through the scanner element, some particles are lost or trapped in pockets and particularly in the bottom of the second chamber because of the loss of the stirring action. A change in the volume of the sample suspension is experienced. Some sample is lost during each execution of the data taking sequence. As a result, only a limited number of data points can be taken on each sample with a sufficient degree of reliability. Further, large fractions of the total sample cannot be measured in any one pass through the aperture, this being a requirement at the large diameter end of the size distribution where the particle population density is normally low. In addition, recovery of the total sample at the completion of the analysis is not possible because each fraction of the sample becomes contaminated when contacting the mercury in the manometer. Full recovery of the sample is particularly important when working with expensive or potentially hazardous materials. Moreover, samples which react chemically with the mercury cannot be analyzed, thereby limiting use of the apparatus to samples which do not have such reaction. Beyond that, the scanner element is difficult to clean and maintain.

SUMMARY OF THE INVENTION One of the objects of this invention is to provide improved aperture vessel construction for fluid-suspension particle analyzers.

A further object of this invention is to provide an aperture vessel which will minimize particle loss and entrapment and virtually prevent a volumetric change of the sample suspension.

Another object of this invention is to provide an aperture vessel which will enable virtually an unlimited number of data points to be taken using the same sample, in addition to enabling large fractions of the total sample to be measured in any one pass through the vessel, both with a high degree of precision and accuracy.

Still another object of this invention is to provide an aperture vessel characterized by essentially a closed system, and free of a mercury manometer, so as to eliminate sample contamination, enable recovery of essentially the total sample at the completion of the analysis, and enable use of samples which heretofore were excluded because they would normally react with mercury.

An additional object of this invention is to provide an aperture vessel which is much easier to clean and maintain than the prior art devices.

Other and further objects of this invention will become apparent during the course of the following description and by reference to the accompanying drawings and appended claims.

The foregoing objects can be attained with an aperture vessel arranged for recycling the analyzed samples. The vessel is equipped with a stirrer and a round bottom sample beaker for improving stirring efficiency of the fluid suspension. An upright tubular aperture chamber having open top and bottom ends and a planar side wall portion is secured to a wall of the sample beaker so that an aperture therein communicates directly with the fluid suspension. A pair of electrodes are secured on opposite sides of the aperture in contact with the suspension and are wired to a Coulter type instrument. A large-fraction sample volume-measuring bulb is provided which is either incorporated within the tubular aperture chamber or piped in series beyond said chamber, thus allowing a large number of data points to be taken before recycling. Atmospheric and vacuum valving means are connected to the open top of the aperture chamber so as to eliminate the mercury manometer. Other valving means is o eratively associated with the bottom end of the aperture chamber, and with the series-connected volume-measuring bulb when used, which enables recovery of the analyzed sample below the aperture. A detachably mounted transfer flask receives the recovered sample, thus enabling sample recycling into the sample beaker. The aperture vessel is so contoured that particles which normally tend to settle out of an unstirred solution beyond the aperture will settle in a location which is amply washed free of these particles by the suspension fluid during each recycling operation. Hence, the original sample suspension is restored prior to each run.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional elevation view of one embodiment of the aperture vessel of this invention shown connected diagrammatically to a particle signal analyzer.

FIG. 2 is an enlarged lateral cross-sectional view of the FIG. I embodiment.

FIG. 3 is an enlarged vertical cross-sectional view of the FIG. 1 embodiment.

FIG. 4 is a cross-sectional elevation view of another embodiment of this invention and is otherwise similar to that of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, FIG. 1 shows an electronic particle analyzing apparatus which includes a simplified embodiment of an aperture vessel generally designated as 10, the details of which are also shown in FIGS. 2 and 3. Aperture vessel includes two glass members, each designated generally as sample chamber 11 and aperture chamber 12. Sample chamber 11 is a beaker 13 of say 250 ml. capacity which, when sample particles have any tendency whatsoever of settling out of the fluid suspension 14, is fitted with a glass stirrer 1S and adapted with a round bottom 16 to maximize the uniformity of particle distribution in suspension fluid 14 due to stirring action.

Aperture chamber 12 is an upright tubular member 17 having an open bottom 18 and a tapered open mouth 19 at its upper end. Tubular member 17 also has a planar side wall portion 20, the edges of which are secured to an elongated upright slot 21 in the side wall of beaker 13 so that a fluidtight joint results. The outer face of Wall portion 20 is located to generally conform to the inner wall contour of beaker 13 so as not to form a pocket which would trap particles.

Aperture chamber 12 is provided with an aperture or orifice 22 extending laterally through the lower end of planar side wall portion 20 of tubular member 17, just above the bottom of beaker 13, thereby establishing a fluid passageway for flowing fluid suspension 14 from sample chamber 11 into aperture chamber 12. The sidewall location of aperture 22 reduces aperture clogging by particles and debris in fluid suspension 14, the clogging normally having an adverse effect on the accuracy of particle count and characterization. Aperture clogging is further minimized when using stirrer because the stirrer produces a circular swirling action in fluid suspension 14 as it is directed over the beaker round bottom 16 and then upward perpendicular to the aperture flow axis, thereby keeping aperture washed clean of clogging material.

Aperture 22 may be located in a sapphire wafer 23 which is secured in wall portion 20 and has dimensions related to particle size. Various factors dictate aperture size but generally, particle dimensions are preferably limited to a range of about l to about 50 percent of aperture diameter. Presently, aperture diameters range up to about 600 microns and greater but are not limited thereto. The length of the aperture, measured along its axis, is about 75 percent of the diameter. For further discussion on particle size and detection and on construction details of the aperture, glassware, etc., see the above noted Coulter U.S. Pat. No. 2,985,830.

Aperture vessels of the present invention may be used with a variety of particle analyzers as long as they include means for enabling the particles to be characterized by an external analyzer during particle passage through an aperture. One such apparatus may operate on the electro-optical principle where radiant energy generating and detecting means is imaged on aperture 22 and the resulting pulse signal transmitted to an external analyzer. Another type apparatus may be the Coulter electronic type where, as herein, a pair of platinum electrodes 24, 25 are secured insulatively from each other on opposite sides of aperture 22 and in contact with a fluid suspension such as 14 to form the particle detector. For convenience, electrode 24 is located in sample chamber 11 on the outer surface of planar wall 20 of tube 17; and electrode 25 is located in aperture chamber 12 along the interior wall of tube 17 opposite wall portion 20. Electrodes 24,25 are connected by way of platinum wires 26,27 to terminals 28,29, respectively. For convenience, terminals 28,29 are secured to the exterior wall of tube 17 and are circuited by way of leads 39,31 to particle signal analyzer 32.

Particle signal analyzer 32 may consist of the instrument portion of the above noted commercially available Coulter Counter, Model B-M, or equivalent. Or it may be other commercially available signal and multiple channel instruments adapted for use with changes in electrical characteristics across electrodes 24, 25 relative particle characteristics as the particles pass through aperture 22.

Still referring to FIG. 1. aperture vessels of the present invention may also be used with particle analyzers during test runs on either a volume or a time basis, and when run on a volume basis, may be done with and without external fluid suspension metering devices. If it is decided to make volume runs without external fluid metering devices, then advantage may be taken of one of the features of the present invention. That is, the incorporation of either an elongated, or a squatty (not shown), upright glass volume-measuring bulb 33 in the tubular member 17 of aperture chamber 12, thereby eliminating the initial cost of a fluid metering device as well as operating and maintenance costs thereof. Volume-measuring bulb 33 may be incorporated in tube 17 between open top 19 and downstream of, or otherwise beyond, aperture 22 and preferably above electrode 25. In this manner, a predetermined volume of fluid suspension 14 may be measured during passage through aperture 22, but not until the electrical detection circuit is completed between electrodes 24,25 by said suspension, and before leaving aperture chamber 12. Volumemeasuring bulb 33 is adapted to accommodate large fractions of the total sample capacity of beaker 13, say about -100 ml. capacity, a substantial increase over the 2 ml. fraction handled by the commercially available Coulter Counter, Model B, mercury manometer metering device. This enables a large number of data points which can be taken during any one run, and these with greater precision and accuracy than heretofore.

Volume-measuring bulb 33 may be calibrated with marked graduations 34,35 to indicate to an attendant that an initial volume and a final predetermined volume, respectively, have been attained. When the fluid suspension under test rises to mark 34, the particle counting procedure should be started; and when the fluid continues to rise and reaches mark 35, then the particle counting procedure should be stopped. There may be as many calibration markings between marks 34-35 as desired.

Although not shown on the drawings, conventional wire electrodes may be inserted through the glass wall of volumemeasuring bulb 33 at marks 34 and at 35 and wired to the start and stop terminals of the Coulter Counter noted above. These would automatically perform the start and stop counting functions presently performed by the start-stop electrodes in the Coulter mercury manometer, Similarly, photo generating and photo level detecting devices of conventional construction may also be mounted at the calibrated volume levels in lieu of markings 34,35. These would be activated by the rise of the sample suspension and initiate the aforesaid start and stop count functions.

Further to aperture vessel construction, a hollow glass tee member 36 with a tapered open-bottomed leg 37 is fitted into the open top end 19 of aperture chamber 12. Open tee branches 38,39 are fitted to valves 40,41, which are connected to the atmosphere and a source of vacuum, respectively, the latter being not shown. In addition, recovery valve 42 is connected to the bottom of aperture chamber tube 17 and consists of a flexible plastic tube 43 connected to the bottom end 18 of tube 17 which is fitted with a pinch clamp 44. Finally, a transfer flask 45, such as a glass inverted Ehrlenmyer flask (with a tube on which flexible plastic tubing and a pinch clamp is placed all not shown is adapted to receive and recycle the sample fraction which passes through aperture 22 and through recovery valve 42 as described below.

In operation, it is presumed that a sample suspension 14 of known particle dilution has been adequately prepared with a conductive fluid as the suspension media. It is further presumed that atmospheric valve 40, vacuum valve 41 and recovery valve 42 are all closed.

First, wash the sample suspension 14 into the beaker of sample chamber 11 and initiate stirrer as required to maintain a uniform distribution of the particular particles in the fluid suspension. Then apply vacuum to aperture chamber 12 by opening valve 41. The sample suspension 14 will contact electrode 24 and be drawn through aperture 22 and then brought into contact with electrode 25. At this point the current flow between electrodes 24,25 has stabilized and particle counting is ready to begin.

The sample suspension 14 will rise in tube 17 and when it gets to the lower calibration mark 34 in volume-measuring bulb 33, the particle counting procedure is started by either manually or automatically starting the Coulter Counter, or equivalent When sample suspension 14 rises to the upper mark 35, the particle counting procedure is stopped, either manually or automatically. At this point both the particle size range indicated and the particle count registered on the Coulter counter should be recorded.

Next, close vacuum valve 41 and open atmospheric valve 40 and recovery valve 42, thereby to vent aperture chamber 12 to atmosphere and flush the fraction of sample suspension into transfer flask 45. Any particles which dropped out of the unstirred suspension beyond aperture 22 would have fallen into the bottom end 18 of aperture tube 17 and then been washed into flask 45 without loss.

Flnally, recycle the sample from flask 45 into sample chamber 11 by opening the pinch clamp on flask 45, being careful to rotate flask 45 to cause a swirling action action therein as the sample fraction is washed back into sample chamber 11. Thus, it can be seen that as large a sample frac tion may be used as is desired and as many sample recycles may be accomplished with the same fluid suspension as is desired, thereby realizing a virtually unlimited number of data points that can be taken with the same sample suspension.

When recycling is completed, or if recycling is not desired, virtually the complete sample suspension may be reclaimed after passing through recovery valve 42 without having been contaminated. This is an important feature when dealing with expensive or potentially hazardous materials, or those requiring subsequent processing.

Turning now to FIG. 4, there is shown an electronic particle analyzer which includes another embodiment of an aperture vessel generally designated as 46. Aperture vessel 46 is similar to, but provides more precise measurements than, aperture vessel 10 for reasons noted below. Aperture vessel 46 includes three major glass members, each designated generally as sample chamber 47, aperture chamber 48 and volume-measuring means 49, rather than two such members. Construction details of sample chamber 47 and the lower portion of aperture chamber 48 are substantially similar to comparable portions of aperture vessel 10 shown in FIGS. 2 and 3, however the volume-measuring means piping is different.

Sample chamber 47 is a round bottom beaker 50 which receives the sample fluid suspension 51 and, when required, is equipped with a glass stirrer 52 for reasons noted above.

Aperture chamber 48 is a generally upright tubular member 53 having an open bottom 54 and a downward inclined upper end 55 having a tapered open mouth 56 projecting upright from 55. Tubular member 53 also has a planar side wall portion 57, the edges of which are secured to an elongated upright slot 58 in the side wall of beaker 50 so that a fluidtight joint results.

Aperture chamber 48 is adapted with an aperture or orifice 59in the lower end of the planer side wall 57 of tube 53 so that its flow axis is lateral to the vertical axis of beaker 50 and tube 53. Aperture 59 may also be located in a sapphire wafer 60 which is secured to the side wall 57 and is located and dimensioned as noted above.

Aperture vessel 46 may also be used with either electronic or electro-optical particle analyzers the same as aperture vessel 10. However, the Coulter electronic type of apparatus requires the use of electrodes. For this reason, a pair of platinum electrodes 61,62 are secured insulatively from each other on opposite sides of aperture 59 and in contact with a fluid suspension such as 51 to form the particle detector herein. For convenience, electrode 61 is located in sample chamber 47 on the outer surface of wall 57 of tube 53; and electrode 62 is located in aperture chamber 48 along the upper interior portion of tube 53. Electrodes 61,62 are connected by way of platinum wires 63,64 to terminals 65,66, respectively. For convenience, terminals 65,66 are secured to the exterior wall of tube 53 and are circuited by way of leads 67,68 to particle signal analyzer 69, the analyzer being one of the types of instruments noted above.

Still referring to FIG. 4, aperture vessel 46 may also be used with particle analyzers during test runs on either a volume or a time basis. The volume basis is provided by means 49 which consists of either an elongated, or a squatty (not shown), upright glass volume-measuring bulb that is supported by beaker 50 and branched in series with aperture chamber 48. The latter is accomplished by extending the downward inclined upper end 55 of aperture chamber tube 53 to upper inlet end 71 of bulb 70, thus placing bulb 70 beyond aperture 59 and preferably below the highest point in aperture chamber tube 53. Lower outlet end 72 of bulb 70 is piped to recovery valve means yet to be described. In this manner, a predetermined volume of fluid suspension 51 may be measured during passage through aperture 59 only after the electrical detection circuit is completed across electrodes 61,62 by said suspension. Equally important, however, is the fact that fluid head pressure in aperture chamber 48 is maintained substantially constant on the downstream side of aperture 59 because fluid suspension 51 must rise to, but does not exceed, level 73 whenever test runs are made. This substantially constant fluid head pressure enables aperture vessel 46 to generally make more accurate and precise time basis test runs than aperture vessel 10, inasmuch as a change in pressure differential across aperture 59 (and 22) affects the flow rate of fluid suspension 51 (and 14) therethrough. Such a change would have an effect on assumed particle dilution during any given increment of time.

Volume measuring bulb 70 may be calibrated with marked graduations 74,75 to indicate to an attendant that an initial volume and a final predetermined volume, respectively, have been attained. When the fluid suspension under test rises to mark 74, the counting procedure should be started; and when the fluid rises to mark 75, the counting procedure should be stopped. There may be as many calibration markings between marks 74-75 as desired. The actual starting and stopping of the counting procedure may be done either manually or automatically as noted above.

Further to aperture vessel 46 construction, a hollow glass tee member 76 with a tapered open-bottomed leg 77 is fitted into the open top end of 56 of aperture chamber 48. Open tee branches 78,79 are fitted with valves 80,81, which are connected to the atmosphere and a source of vacuum, respectively. In addition, recovery valve means 82 is provided which comprises valve 83 connected to the bottom of aperture tube 53 and valve 84 connected between lower end 72 of volumemeasuring bulb 70 and an open-ended lateral 85 extending upward from the side wall of aperture tube 53. Valve 83 consists of a flexible plastic tube 86 connected to bottom end 54 of aperture tube 53 and is fitted with pinch clamp 87. Valve 84 also consists of a flexible plastic tube 88 which is fitted with pinch clamp 89. Tube 88 is connected to the outside of end 72 of bulb 70 and the inside of lateral 85, thereby allowing free passage of fluid suspension 51 without trapping any particles in lateral 85. Finally, a transfer flask 90, the same as transfer flask 45, is adapted to receive and recycle the sample fraction which passes through aperture 59 and then through recovery valve means 82 as described below.

In operation, it is presumed that a sample suspension 51 of known particle dilution has been adequately prepared; that atmospheric valve 80, vacuum valve 81 and recovery valve means 82 are all closed; and that sample suspension 51 has been washed into the beaker of sample chamber 47 and that stirrer 52 has been initiated as required. First, apply vacuum to aperture chamber 48 by opening valve 81. Sample suspension 51, already in contact with electrode 61, is drawn through aperture 59 and into contact with electrode 62. At this point the current flow between electrodes 61,62 has stabilized and particle counting may begin.

in the meantime, sample suspension 51 rises in tube 53 to its maximum level indicated at 73, then spills over continuously into inclined tube 55 and volume-measuring bulb 70. When fluid suspension 51 rises to the lower calibration mark 74 in volume measuring bulb 70, the particle counting procedure is started, and when fluid suspension 51 rises to mark 75 counting is stopped, both as noted above. At this point, record the particle size range indicated, and the particle count registered on, particle signal analyzer 69. Next, close vacuum valve 81 and open atmospheric valve 80 and recovery valve means 82, thereby to vent aperture chamber 48 to atmosphere and flush the fraction of sample suspension 51 into transfer flask 90. Any particles which drop out of the unstirred suspension beyond aperture 59, either by way of aperture tube 53 or by way ofinclined tube 55 and volume-measuring bulb 70, would have fallen into bottom end 54 of aperture tube 53 and bottom end 72 of bulb 70, respectively, and then been washed into transfer flask 90 without loss when recovery valve means 82 is opened.

Finally, recycle the sample fraction from flask 90 into sample chamber 47 in the same manner as noted above for flask 45. When recycling is completed, or if recycling is not desired, virtually the complete sample suspension may be reclaimed after passing through recovery valve means 82 without having been contaminated. As noted above, this is an important fea ture when dealing with expensive and potentially hazardous materials, or those requiring subsequent processing.

I claim:

1. ln fluid-suspension particle analyzers, an aperture vessel comprising:

a. a sample chamber adapted to contain a predetermined amount of fluid and having particles to be analyzed suspended in said fluid,

b. an upright tubular aperture chamber having upper and lower open ends and further having a side wall portion secured in contact with a wall of the sample chamber,

c. an aperture in the side wall of the aperture chamber which is adapted to pass the fluid-suspended particles between the sample and aperture chambers, d. means including first and second valve means operatrvely associated with the respective upper and lower ends of the upright aperture chamber for enabling a predetermined amount of sample suspension to be passed through the aperture by external forces acting under control of the first valve means, said second valve means further enabling undiluted recovery of substantially all of the sample suspension fluid and both suspended and unsuspended particles passed through the aperture without disassembling said aperture vessel, said means (d) also enabling recycling the recovered undiluted sample to the sample chamber, if desired, and

e. means for enabling the particles to be characterized by an external analyzer during particle passage through said aperture.

2. The aperture vessel of claim 1 wherein the aperture is sized to approximate microscopic particles.

3. The aperture vessel of claim 1 wherein means (d) includes:

.l. a volume-measuring bulb beyond the aperture into which the sample suspension flows for determining the passage of said predetermined amount of sample suspension through the aperture.

4. The aperture vessel of claim 3 wherein the volume-measuring bulb is incorporated in the tubular aperture chamber.

5. The aperture vessel of claim 3 wherein the volume-measuring bulb is separated from the upper end of said tubular aperture chamber, but piped thereto, in such manner as to receive a spillage therefrom while maintaining a constant head pressure and constant volume of sample suspension in the aperture chamber during particle characterization.

6. The aperture vessel of claim 3 further including:

.1 1. means for indicating an initial volume or one or more other predetermined volumes, of sample suspension in said bulb.

7. The aperture vessel of claim 3 further including:

.12. means for signaling the particle analyzer in response to a fluid level corresponding to an initial volume, or one or more other predetermined volumes of sample suspension in said bulb.

8. The aperture vessel of claim 1 wherein means (e) is adapted to enable particle size, particle count, or both such properties, to be characterized by said analyzer.

9. The aperture vessel of claim 1 wherein means (e) includes:

.l. a pair of spaced apart electrodes with individual electrical leads insulated from each other, each said electrode secured on opposite sides of said aperture for enabling particle characterization based on electrical properties of the sample suspension passing through said aperture. 

1. In fluid-suspension particle analyzers, an aperture vessel comprising: a. a sample chamber adapted to contain a predetermined amount of fluid and having particles to be analyzed suspended in said fluid, b. an upright tubular aperture chamber having upper and lower open ends and further having a side wall portion secured in contact with a wall of the sample chamber, c. an aperture in the side wall of the aperture chamber which is adapted to pass the fluid-suspended particles between the sample and aperture chambers, d. means including first and second valve means operatively associated with the respective upper and lower ends of the upright aperture chamber for enabling a predetermined amount of sample suspension to be passed through the aperture by external forces acting under control of the first valve means, said second valve means further enabling undiluted recovery of substantially all of the sample suspension fluid and both suspended and unsuspended particles passed through the aperture without disassembling said aperture vessel, said means (d) also enabling recycling the recovered undiluted sample to the sample chamber, if desired, and e. means for enabling the particles to be characterized by an external analyzer during particle passage through said aperture.
 2. The aperture vessel of claim 1 wherein the aperture is sized to approximate microscopic particles.
 3. The aperture vessel of claim 1 wherein means (d) includes: .1. a volume-measuring bulb beyond the aperture into which the sample suspension flows for determining the passage of said predetermined amount of sample suspension through the aperture.
 4. The aperture vessel of claim 3 wherein the volume-measuring bulb is incorporated in the tubular aperture chamber.
 5. The aperture vessel of claim 3 wherein the volume-measuring bulb is separated from the upper end of said tubular aperture chamber, but piped thereto, in such manner as to receive a spillage therefrom while maintaining a constant head pressure and constant volume of sample suspension in the aperture chamber during particle characterization.
 6. The aperture vessel of claim 3 further including: .11. means for indicating an initial volume or one or more other predetermined volumes, of sample suspension in said bulb.
 7. The aperture vessel of claim 3 further including: .12. means for signaling the particle analyzer in response to a fluid level corresponding to an initial volume, or one or more other predetermined volumes of sample suspension in said bulb.
 8. The aperture vessel of claim 1 wherein means (e) is adapted to enable particle size, particle count, or both such properties, to be characterized by said analyzer.
 9. The aperture vessel of claim 1 wherein means (e) includes: .1. a pair of spaced apart electrodes with individual electrical leads insulated from each other, each said electrode secured on opposite sides of said aperture for enabling particle characterization based on electrical properties of the sample suspension passing through said aperture. 